Fuel supply for internal combustion engines



FUEL SUPPLY FOR INTERNAL COMBUSTIONENGINES Filed April 19, 1938 lnvebtors Patented Sept. 29, 1 942 2,297,238 FUEL SUPPLY ron INTERNAL COMBUSTION ENGINE Franz Neugebauer, Allach, near Munich, and August Lichte, Dessau-Alten, Germany; vested in the Alien Property Custodian Application April 19, 1938, Serial No. 202,934

.In Germany May 22, 1937 1 Claim.

Our invention relatesto the supply of fuel to internal combustion engines and has particular reference to means for freeing the liquid fuel injected into such engines from the air admixed to it.

It is well known' that air present in afuel supply system leading from the fuel tank through a delivery pump and an injecting pump to the engine, if entering the working chambers of the injection pump, injection pipes and nozzles, is liable to disturb the operation of the system.

It is a particular object of our invention to construct a system of fuel supply in such manner that before starting operation of the engine as well as during normal operation any air present in the fuel fed to the injection pump is separated from the fuel in the most perfect possible manner.

Means have already been provided for separating the air from liquid'fuel flowing from a delivery pump to an injection pump. As a rule these separating means merely removethe greater part of the air or other gases which may be admixed to the fuel, before it reaches the injection pump and engine. It has however been found that even if such separating means are provided, disturbances of the injection by the air in the fuel may occur. This is due to the fact that the small quantities of air, which were-not separated out by the separating device, will gradually collect in the low pressure space, of the injection pump, until finally a larger quantity of collected air passes into this pump.

In order to avoid this drawback, we provide a connection, through which the fuel supplied to. the injection pump in excess and therefore not entering the engine is returned to the suction side of the delivery pump, from which it can now be conveyed afresh to the separating device and from there to the injection pump.

Our invention thus comprises a method of air and fuel separation, in which the fuel is permanently kept circulating from the delivery pump through the separating device tothe injection pump and back to the delivery pump, so that also small quantities which may'have been left in thefuel during its first passage through the separating device, are now prevented from collecting in the low pressure space of the injection pump, being permanently carried back by the fuel returning into the separating device, to be there removed. We thereby obtain a highly eflicient separation of the air, which will prove useful also in the case where fuel is fed to the 55 space. I of the injection pump, are carried along injection pump under a considerable pressure above normal.

In order to remove the air, which before the start of the engine fills the fuel pipes between the delivery pump and the engine, as completely as possible from all parts of the pipes and more especially also from the injection pump, we may further connect the space on the low pressure sideof the injection pump, which contains fuel, with the separating device by means of a separate pipe, through which'this air may escape into the separating device and into atmosphere.

In the case of an aero'engine provision has to be madefor' the inclined position of the longitudinal axis of the aeroplane when the aeroplane rests upon. the ground, the tailof the plane being lower than the nose. No part of the fuel line should make with the longitudinal axis of the craft an angle which is smaller than the angle which this axis makes with the horizontal in the taildown position. If care is taken to avoid this, the fuel is prevented from accumulating in the line and from blocking it, and therefore air can be successfully separated from the fuel in the tail down position of the plane. I

In the drawing afllxed to this specification and forming part thereof an embodiment of our in.- vention is illustrated by way of example in a diagrammatic elevation, part1y in vertical section. Referring to the drawing, I is a fuel tank, 2 indicates the internal combustion engine, 3 is a hand-operated pump-and 4 is the fuel pump driven by the engine. 5 is the air and fuel separating device, 6 is the injection pump. From the end of the low pressure space l6 of the injection pump, which is opposite the point where the pipe I coming fromthe separating device ends,

a pipe .8 .leads to the pressure regulating andcheck valve 9 and from here back to-the suction side of the fuel pump 4.

During normal operation this system operates in such manner that fuel is forced by the pump 4 through pipe l0 into the separating device 5, to be freed in this device from the'greater part of the air admixed to it. which can escape into atmosphere through a pipe ll, so thatas a rule fuel substantially free from air flows through pipe I to the injection pump i. That part of the fuel conveyed by pump 4," which exceeds the quantity to be injected into the engine, returns through the pipe 8 to the fuel pump in orderto be conveyed afresh through the separating device to the injection pump. The small quantities of air which have still entered the low pressure by the fuel in excess returning through pipe 8 andv are carried back to the suction side of the fuel pump 4. This part of the fuel, which still contains some air, .is then returned togetherwith fresh fuel, by the pump 4 through pipe In to the separating device 5, to be there freed again from air before being fed again to the injection pump 6. Since this circulation is permanently kept going during the operation of the engine, any accumulation of air or other gaseous admixtures, which might disturb the injection, in the low pressure space of the injection pump 6 is avoided altogether.

In order toexplain the mode of action of the invention before the engine of an aircraft is started, let usaissume that the longitudinal axis 11-1! of thej'engine 2 and the longitudinal axis :r-a: of the injection pump extend in parallel to the longitudinal axis of the craft and that the position of these axes :c-a: and 11-1 in the drawing corresponds to the tail down position of the craft on the ground. During normal fiight these axes take up the horizontal position illustrated by the line z-z, which makes with the tail down position 11-1! the angle a. The direction of flight is indicated bythe arrow parallel to line 2-2.

Before the engine is started, no fuel, but only air is present in the pipe I, the separating device 5, the pipe I, the injection pump 6 and the return pipe 8. Now first the casing of the separating device 5 is filled with fuel by means of the handpump 3. When the fuel. after having already been freed from most of the air admixed toit through the action of the separating device,

reaches the pipe 1, it will fiow through this pipe into the low pressure space l6 of the injection pump 5, gradually displacing the air filling this space. In order to enable the air to escape from the pipe I and the low pressure space ll of the injection pump, as narrow pipe II is connected to that point II of the space Ii, which is the highest in the tail down position of the craft and up to which the fuel rises only after having filled the suction ports ii of all the cylinders of the in- :Iection pump. The pipe I! leads back to the separating device 5, ending at the point I4 above .the end of the pipe I. The nin l3 conducts the air displaced by the fuel from the pipe I and the space I into the top part of the separating device so that it can escape through the pipe II. In order to guarantee a reliable exhausting of with air-free fuel by preventing the air exhaustion from taking place.

Preferably the pipe 1 leading from the air separating device to the injection pump is arranged in a similar manner in order to prevent any residual fuel from remaining in this pipe, when the fuel line is emptied, which might prevent or hinder the air from escaping when fresh fuel is filled in. As long as the craft occupies during fiight a position, in which the end ll of the pipe l3 lies below the fuel level in the separating device 5, a small fraction of the fuel flows through this pipe ii to the injection pump. In

all other cases, for instance during a steep climb, this pipe is filled with fuel up to a corresponding level so that the operation of the engine is not impaired by the presence of the pipev I3.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described for obvious modifications will occur to a person skilled in the art.

We-olaim:

An air eliminating system for the fuel supply to an internal combustion engine provided with a fuel pump and an indection' pump, said system comprising, in combination with said fuel pump and injection pump, an air and fuel separating device between the two pumps, and a fuel circulating system interconnecting said fuel pump, device, and injected pump composed of a first conduit for conducting fuel from said fuel pump to said device, a second conduit for conducting fuel from said device to said injection pump, a third conduit for conducting excess fuel from said in- ,jection pump directly to said fuel pump for recirculation therethrough, and a fourth conduit connecting said injection pump and said device for releasing air entrapped in said injection D p.

AUGUST LICHTE.

FRANZ NEUGEBAUER.- 

